This invention relates to a label coated with a pressure sensitive adhesive that will decorate and conform to the surface of polyethylene, polyethylene terephthalate, polyvinyl chloride, polypropylene and other flexible plastic containers, and having advantages of being deformable, non-shrinking, and improved adhesion in a manner that is essentially a permanent part of the system, similar in appearance and mechanical performance to the surface of the substrate itself.
The packaging industry has increasingly evolved to the use of flexible materials in place of rigid glass and metal in containers for both solid and liquids. Where items of oil and water based fluid categories, as for example, milk, beer, catsup, mustard, sugar syrups, soaps, cooking oil or motor oil, to name a few, were packaged in glass or metal containers, they are now more often packaged in plastic containers. Certain of these containers being polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and the like are flexible by their nature and are intended to be deformable in that the container may change its shape during the course of its manufacture, processing, or use cycle, and upon removal of the deforming force, return to its original shape or dimension. This, of course, has advantages of design, manufacture and display as well as in protection and dispensing of the products. It also has certain disadvantages, one of these being that conventional labels of paper do not expand and contract uniformly with the bottle substrate during hot filling operations, and do not flex or deform during mechanical handling and end-use without wrinkling, creasing, tearing or otherwise suffering permanent damage to the label.
Previously, labels for deformable and flexible bottles, packages or parts has been approached generally in three ways; (1) by printing directly on the substrate, (2) by using flexible polyvinyl chloride labels, and (3) by heat transfer printing and decorating. Each of these methods, in addition to being more expensive than conventional paper labels, has other drawback as well.
Direct printing, as for example that system disclosed in the U.S. Pat. No. 3,249,044, has obvious limitations of design and ability to be incorporated into a high volume production line manufacturing method. Using vinyl (PVC) films in deformable labels is well known and is practiced effectively in a variety of application. Vinyl, however, has chemical and physical characteristics which are limiting in several notable respects. Polyvinyl chloride in unmodified form, is rigid and must be highly plasticized and stabilized to be sufficiently flexible and stable for use in application such as deformable label film. The physical and chemical characteristics of these highly modified vinyl films result in limitations of film thickness, dimensional stability during hot-filling or other thermal operations, compatibility (migration of plasticizers and stabilizers) with adhesives and substrates and in shelf life. Heat transfer printing and decoration, as for example that disclosed in British Pat. No. 1,487,749, while faster than direct printing is still slow relative to current general purpose labeling lines.
Polyethylene films have not previously been used as deformable labels.
Prior to this time it was generally accepted that the polyethylene homopolymer films were not suitable to the printing, handling and adhesion requirements of this demanding application. I have now discovered that a label system comprised of certain polyethylene film materials, together with selected adhesive as provided in the later sections of this specification, and combined in the manner of this invention, does indeed provide a label that is suitable for use in the deformable label application and that is unique in its ability to function essentially as an integral part of the package itself, allowing bottles, packages, parts and the like, not only to be pre-labeled prior to hot-filling or other thermal or mechanically abusive operations, but also to provide the same resistance to thermal, and/or mechanical deformations, as well as chemical resistance throughout an extended use and shelf-life period.